Shrinkage method for knitted fabrics



Dec. 8, T953 J. HAMILTON ET AL 2,661,526

SHRINKAGE METHOD FOR KNITTED FABRICS Filed June 19, 1950 3 Sheets-Sheet l m}. b mcm new M34 who) Llcra mas Dec. 8, 1953 J. HAMILTON ET AL SHRINKAGE METHOD FOR KNITTED FABRICS Filed June 19, 1950 3 Sheets-Sheet 2 BIG. 6

I'll/m5 der; Jr:

John Hamilton Xe.

Dec. 8, 1953 J. HAMILTON ETAL SHRINKAGE METHOD FOR KNITTED FABRICS 3 Sheets-Sheet 3 Filed June 19, 1950 z wflmme s W W Patented Dec. 8, 1953 SHRINKAGE METHOD FOR KNITTED FABRICS John Hamilton, Oakford, and Arthur A. Meder,

Jr., Penllyn, Pa.,

assignors to Proctor &

Schwartz, Inc., Philadelphia, Pa., a corporation of Pennsylvania Application June 19, 1950, Serial No. 168,952

Claims.

" This invention relates to treatment of knitted fabrics, and more particularly to treatment of tubular knitted fabrics to prevent or eliminate objectionable shrinkage of garments made therefrom. By a tubular knitted fabric is meant one which is knitted in tubular form or one which is knitted in fiat form and then converted to tubular form.

Shrinkage has long been a problem in the textile industry, and much effort has been directed toward reduction thereof both in woven and knitted fabrics. Th problem has been particularly troublesome in the case of knitted fabrics, and in fact shrinkage has prevented use of such fabrics in many fields.

Referring particularly to knitted fabrics, as

they come from the knitting machine such fab rics are subjected to treatment known as wet processing which includes scouring, bleaching and dyeing. As the fabric comes from the knit ting machine it'has some potential fibre shrinkage but this disappears in the wet processing and is of no concern. However, the wet processing subjects the fabric to severe tensional forces lengthwise and produces (1) great distortion of the knitted stitches and (2) slight fibre and yarn stretch. We have discovered that later shrinkage of a garment made from such fabric is due primarily to the stitch distortion, and secondarily to the fibre or yarn stretch. While the latter factor is greater in wool fabric than in cotton fabric, it is always of much lesser effect than the stitch distortion which is the primary cause of shrinkage. With the stitch distortion present the fabric is increased in length and decreased in Width; that is tosay the fabric is stretched. Laundering of a garment made from such fabric causes especially tubular knitted fabric, to eliminate objectionable shrinkage thereof.

Another object of the invention is to provide such a method which is applicable to all kinds of knitted fabrics composed of either natural or synthetic fibres, or mixtures thereof.

In accordance with the present invention, a knitted fabric is treated in a manner to bring about a normal condition of the fabric, As

used in this specification and in the appended claims, the word normal means a condition in which the fabric has zero potential shrinkage both lengthwise and widthwise. This may be said to be a zero-zero condition, and it is the condition which would exist if a fabric were simply washed. In this condition of the fabric, the stitches have a certain shape and size, and the fabric has certain dimensions. The departure from this condition is what permits shrinkage. As the fabric goes through the wet processing, during which it is in a soft, Wet and very elastic state, the stitches are elongated longitudinally and narrowed widthwise due 'to the tensional forces acting longitudinally or lengthwise of the fabric. Thus the stitches are distorted from their normal shape and size, and the fabric as a whole is distorted accordingly, being stretched longitudinally and narrowed transversely or widthwise. Upon ordinary drying and other usual treatment such as calendering, the fabric remains in a distorted condition. As the fabric dries the stitches acquire a distorted set, because ordinary treatment does not cause or allow the fabric to become normal.

In order effectively to eliminate shrinkage of arments made from knitted fabric, it is necessary to convert the fabric and its component stitches or loops substantially to the normal condition prior to the making of garments therefrom. We have discovered that this result can be achieved by a simple method which involves, as its principal step, mechanical collapsin of the stitches in any suitable manner. Where the fabric is treated as it comes from the wet processing, the mechanical collapsing of the stitches is effective to prevent them from acquiring the above-mentioned distorted set. Thus if the collapsing action takes place while the wet fabric is being dried, the yarns are caused to flow freely or slide over one another and the stitches are caused to assume their normal shape. Where the fabric is not treated immediately after the wet processing and the fabric is dried, the stitches will have acquired the distorted set but the treatment .according to the present invention will undo the set and will cause the stitches to assume substantially their normal shape. In such case if there is insufficient moisture in the fabric for highly effective treatment, the fabric may'be moistened prior to the treatment, as by steaming it or subjecting it to a fine water spray. Then the mechanical collapsing of the stitches and simultaneous drying will bring about the desired result. While the moisture content of the fabric may vary widely, experiments hav indicated that a moisture content of about of the weight stretched lengthwise and is narrowed widthwise. of the fabric is preferable. However, the inven- As mentioned above, drying of the fabric in this tion may be practiced with any condition of the condition will cause the stitches to acquire a disfabric exceptabone dry condition. torted set which is not corrected by ordinary The mechanical collapsing of the stitches is 5 treatment of the fabric, such as calendering, etc. more readily, carried out tIaIISVSISEIYj'OI'"Width As previouslyipointed outfit isthisscondition of wise of the-fabric, andfor this reason it is"prethe fabric which is largely responsible for ferred to expand the fabric widthwise as a preshrinkage. The secondary causes of shrinkage liminary to the stitch collapsing treatment. Thesis .correct themselves and are relatively unimpurpose of the widthwise expansionisto change .10., portant. V the distortion of the stitches froma'lengthwiser In the" preferred embodiment of the novel distortion to a widthwise distortion, so that the method of the present invention, the fabric is subsequent stitch collapsingfictieatmenti williabe subirected'flto:widthwise expansion to an extent more effective. to producegenera'l'ly the condition illustrated in Most knitted fabrics are calendered after hav- 'l5 Figss3A an'd-i3BE In this condition, the stitches ing been dried from the wet condition in which are"'elon'gated and'distorted widthwise, and the they come from the wet processing. sinceucalee' fabric-x-isshortened lengthwise. This expansion endering is a stretching operation, it may also is a course condensing action as is apparent from contribute to objectionable shrinkagesu- AfliI 3A? This expansion step may be performed ther feature of the present invention resides in by causing the tubular fabric to pass over a the compensating for. calender.rstretchxby carryi spreader:adevicei'capable ofitexpandihgsthe :faibric ingeoutithe stitch.acollapsing-vtreatmenti:to::such to theedesirednxtentfi. Preferably; theespreader. extent; that 1 the. fabric is: fulledor r com isfofzitliefpusheoff type,- i.l.e.t.one havingwdriven dense'd. inv its general plane-, th'at is 'thezfabricvis rollers. 01'? wheels which engage'xthe outside-sot narrower an'dsl'iorter,tharnnorrnal; Then :the the.tubular:fabric-:adjacent'theaexpandingselescalendering of: thee'fabricfiexpands;-the.fabriccto mentsiof zthe'rspreaderrso-as to push'zthe. fabric normalsize: fronrzthe: spreading;device:v Suchiear device-sis.

Reference-is now made -to: the accompanying generally shown in Fig. 6. drawings; wherein: i ThezWidthWlSG?BXPaHSiOII'iOfi2th fiibli0fi8id6- F S- a dedge viewsp-reapictedz inzFi-gsfln and BBi-xis fiective sto'zchangespectively; of-a1portionrr of a knitted-:fabricrin from lengthwise distortion"2.of-*theustitchesato normalccondition; the'd'ouble headarrow indi widthwise distorti'on'.thereof,. so'as'ibetter toa-cone; eating-z thev1ongitud-inal' or 'lengthwise direction," dition the fabric for. the :subsequentristitch cola Figs:- 2A and QBare-similarwiews of .thcisame lapsingptreatmentn p n f a t r t m s net Referring to Fig. 6, the spreading;;device shown" ofwancl.priortoztreatment in" accordanceavithrthecomprises-2a transverse memberzxl 2::carryingg'suppresent invention ports I 3 andiI hat :its sopposite ends, said:v

Eigsi-BA and .-3Br.are-isimilarrviews of the same ports in turnacarryingzwheels:'orsrollerse'I5,:,, I6: portionrofethe? fabric upon subjection thereofito andil'l, I8 which: -are freely-rotatable OIlithiEiSlPDL-i' widthwise-expansion; which; stepgris preferably. ports; A pair'rofa.poweng-drivemwheels:omrollers; included as; aapart "Ofwt'he treatment priorgtc-tthe: I Stand 2flare :arranged -as shownztor support 1711631- ma-in step involving stitchcollapsing spreader. a-ndntofmoveithe tubular :k'nittedtfabric:

Eigs.:-4A= and 4B; are face; and edge-viewszof thee Z I eoverrandz from xthesspreadens The wheels-d 5:,2 same:portion of' the "fabric-after it hasbeenzsu'be lfieand l 'I,-.,I 8=seat within flangeszmot shown). :on: jected toathe: stitch collapsingtreatment'to such the :wheels 'lfi ifln Apairlofimemberss22trandrd3f anwex-tent thatethe fabric-iis-fulled i; e: na'rhave straight parallel lsections extendingrfrom: rower-and shortertharr normal; Wheels? I 6:: and? I8 substantiallyfiangent theretoa Fig-e 5vis:-a-:view ofathesameeportion .Of? the I'heimembersn-ZZ. andu 23:ha ezcuryedisections: fabric: after. calendering; thereof, it being; then- (not r'visible) extending; :in": p'eripheralzgroovesiJOfI substantially'normalg the -wheels I6+ an'd'IB andzpsecured'rtoathe-esups Fig: .6 is 5a diagrammatic illustration of: aadee ports. I 3; and. I 4.. The -mem'bers .22 andt23'; arer vice which may be-.-employed to expand-1 the! stationary and; there; isesufiicient clearance-bee fab i ;v tween-them and. the:;wheels-s. I fii and"; I 8' sorjasenot Fig, 7 is a1diagrammatic-tor.generalized .illusstozinterferewith free;rotation:'.of said-wheelsz: tratiomofan"apparatuswwhich may,be-employed-v The'vtu-bular knitted :fa-bric-all mQVBS'FlflithBz forithe'istitchecollapsing; treatment; directiomof the-arrow: over-:theespreadenwheels:

Fig; 8 :is 'aicross-sectional yiew :taken .alongy line and between those-wheels andthesdriving. wheels;;v 888 of Fig as illustratedc. As? the fabric approacliesgthefe Fig-j 9-fisr a view illustrating; the calendermgi spr ing; deyicea t sr' in. the; lon itudi a y pfifllld 6O stretchedv condition: showmin lTtig-.12A;. ,Asitzisr Fig: 10iis1 an. illustration supplemental .tol a: drawn:overrtheewheels-a I5 and; I! by: 12118 3131305.- description: hereinafter of .r a specific. examplee-.. he ngewheels -l Brand :2 0;: His sp eafl fi txp dedf Referring more partieularlmto';therdrawings; widthwisei-to: the desired extent;. vAs::i1; leayes: inzFigss 1;A2andr..113.--'v the fabriccis: shown: in the: the-.wheels5l5, ,I1; thevfabri'csismushedzbyawhteels normal .conditi'om the-yarnsi ID: being? disposed: 6 I9; 2.0 overiheewheelsxlfiiiem 'anchont -the so.that .the%'stitches.;II.have arcertain' size and; b6rse22, .23: Duringathissaction, thercourseseare? shapg-gand t :fa-bric- .beingsubstantial-ly -freeeofistraightened.- and. condensed;z andttasrzthe fabric. amt-tension-or stretch whichrcanpermit shrinkeleaves the spreading :device; it:iszinrthesconditicn. age; illustrated-in Fig; 3A&

Ei Sv-ZA'aHd 2Brshow= the conditionl-off the: Followmg' the expansion :step above described:- samefabricnafter. the wet processing: It'lwill be: the ifabric: is; subjected to? the stitch collapsing noted :that the stitcheszortloops: I I areeelongated? treatment t0-':a,-n':eXtent:-'.topr dflc e condition lengthwise: or: longitudinally of-= the: fabrics and? shown -in-iFigsAH-and 4B1 Inthis' condition, thev theyrareanarrowediwidthwise: Due to. this-.con"-' fabric fulled or 'condensed relative to the ditiomof- 'thastitchesgthe fabric:asea; wholeeiss nOTmar1 0OI1'di ti0nzshgwnein pi -1 The niches;

are" substantially normal in shape and size-but there is substantial overlapping and close inter mingling of the stitches, the fabric being narrower and shorter than normal. "Compared to the condition of Figs. lA and'lB, the weight per unit area and the thickness of the fabric material are increased.

The mechanical collapsing of the stitches may be effected by subjecting the fabric to agitation which will produce the desired stitch-collapsing action. While any suitable apparatus may be employed for this purpose, a particular form of apparatus which may be employed is shown in Figs. 7 and 8. A foraminous cylindrical shell 24, open at both ends, is supported for rotary movement about its longitudinal axis within a stationary casing or housing which is also of tubular form and has end openings to accommodate the shell 24. The shell 24 and the surrounding casing 25 are inclined to the horizontal at a suitable angle for a reason which will presently appear. In the specific embodiment illustrated, the shell 24 has flanges 26 and 21 which may be in the form of rings permanently secured to the shell, for example by being welded thereto. As shown in Fig. 8, each of these flanges engages three flanged rollers 28 which are mounted on stationary studs suitably supported within the stationary casing 25. To relieve strain on the said rollers, each of the flanges 25 and 2'! also vided a ring gear 3| which surrounds the shell and is suitably secured thereto. The ring gear meshes with a gear 32 which is on a common shaft with a smaller gear 33. The latter meshes with a gear segment 34 (Fig. 8) carried by a wheel segment 35 which is mounted on a rotary shaft 36. A link 3'! interconnects the wheel segment 35 with a crank wheel 38 provided with gear teeth to mesh with a driving pinion 39 on the shaft of a driving motor 40. By this arrangement, the shell '24 is oscillated about its axis through a predetermined arc.

Heated air is supplied to the casing 25 through an inlet conduit 4| from a source 42 which may comprise an air blower and air heating means. The purpose of'this is to dry a fabric passing through the foraminous shell 24,'a-s described below. As shown in Fig. 8, bafiles 43 are provided in casing 25 so that all of the air will pass through the foraminous shell 24. The air is exhausted through conduit 44.

In operation, the fabric 2| may be fed vertically downward into the upper. end of shell 24. In the specific illustration, the fabric is shown being fed by means of a roll 45 from a wound roll 46. As the shell 24 oscillates, the fabric moves by gravity through the inclined shell, and as it does so it is tumbled or agitated. The particular action in this case is a continual falling of one portion of the fabric onto another, so that there is repeated collapsing of the stitches. As it moves through the shell 24, the fabric is subjected to the drying effect of the heated air so that it is being dried at the same timethat it is being agitated. The stitch-collapsing action thus produced converts the stitches substantially to their normal shape and size as previously described, and causes fulling of the fabric so that it emerges from shell 24 in the condition shown in Figs. 4A and 4B.

Following the above-described treatment, the

fabric is calendered in the usualway. Asshow'n in Fig. 9, in the usual calendering operation,-the tubular knitted fabric 2| passes over a frame or spreader 48 which flattens and smooths the fabric just before it passes between-the pressing or calendering roll-s 41. Usually steam is applied to the fabric as it passes over the spreader 48, as by means of a steam box 49. As the fabric passes over the spreader 4B and between the calendering rolls 4?, it is expanded both widthwiseand lengthwise. The calendering operation is effective to remove the fulling completely or partially, as desired, and to convert the fabric substantially to the condition shown in Fig. 5.. It should be noted that the previous fulling action is in anticipation of the stretching produced by calen dering, and the fabric is actually calendered up to size. After calendering, the fabric as a whole is normal and has substantially zero-zero shrinkage. It should be noted further that while the expansion step of Figs. 3A and 3B is preferred for the reason hereinbefore set forth, this step is not absolutely necessary as the stitch-collapsing treatment alone will sufiice but it takes a greater length of time without the expansion step.

In the practice of the invention, it is readily possible to determine the extent of treatment necessary to produce the normal condition ofthe fabric. For a certain fabric from a particular mill and processed in a particular bleachery, a wash test of a sample after wet processing will show the amount or percentage of potential shrinkage. Such a test merely involves washing the sample, and measuring its width and length before and after washing.

By way of example, the following data is given with respect to actual treatment of a particular fabric according to the preferred form of the present invention. The following may be more readily understood with the aid of Fig. 10 which shows a series of illustrations representing a marked figure on the fabric.

The fabric treated was 1 x 1 rib with a tight stitch, which was knitted on a knitting machine having a 10" diameter head.

After bleaching in the usual wet processing, the width of the tubular fabric in flat form was 8%. From a wash test of a sample, it was determined that zero width for this fabric was 11%", and that the fabric had been stretched longitudinally 17%. By zero width is meant the width of the fabric which it should have for substantially zero shrinkage, i. e. the width prevailing after shrinkage of the bleached fabric by the wash test. The test showed that a 17% reduction from the stretched condition represented normal length. The normal condition is represented at a in Fig. 10, while the stretched condi tion is represented at b. I

The bleached fabric which had been stretched 17% and which had a Width in flat form of 8%. was passed over a course condensing spreader of the type illustrated in Fig. 6, the spreader width being 20". After spreading, the fabric was reduced in length by 30%. This condition of the fabric is represented at c in Fig. 10.

The fabric was then subjected to the stitchcollapsing treatment above described, and when dry its width in flat form was 11" and its length reduction was 22% of its stretched length after bleaching. This condition is represented at d in Fig. 10. It should be noted that at this point the 2 fabric was actually smaller in size than the zero condition indicated by the wash test as above mentioned.

The. fabric was then calendered andfoldedin the usual'mannenin the course of which treatment itwas passed over a calender spreader with a 12" width and a folder spreader of 11 Width.

The cold width of the fabric after calendering was.11%", and the coldlength reduction was 16%. This condition is represented at e in Fig. 10. -It willbe noted that the fabric'was-then substantially in the zero shrinkage condition determined by theabove-mentioned wash testing of a sample-after bleaching.

.Following the above-described treatment, the

fabric was subjected to a wash test to determine its (condition from the standpoint of shrinkage. It wasfound that the fabric had a widthwise shrinkage of about 1% and. a lengthwise shrinkage of about 2%. These figures indicated that the fabric had substantially zero-zero shrinkage, since the low percentages indicated are insignificant'fr'om a practical standpoint. The method of treating knitted fabric accordingto this invention as hereinbefore described, is not only highly eflicient in substantially eliminatingshrinkage but it is extremely simple and inexpensive.

Whilea preferred embodiment of the invention hasbeen described,.it will be understood that the invention is not. limited thereto but may be practiced with such variations as may occur to those skilled in theart. For example, the invention contemplates. any suitable treatment of the fabric which will effect the stitch-col1apsing action, and is not limitedto the specific treatment described.

We claim:

1. A method of treating wet or moist stretched knitted fabric whereof-the stitches are distorted from normalshape, which methodcomprises mechanically collapsing the stitches from their distorted condition to an extent to condense the fabric both lengthwise and widthwise andcause substantial overlapping and close intermingling of L the stitches, thus reducing the fabric to smallerthan-normal size, drying the fabricaconcomttantly with the stitch collapsing action, and calendering the fabric to finish the same and to expand the fabric to its normal size.

2. A method of treating wet or moist longitudinally-stretched knitted fabric whereof the stitches are elongated longitudinally and distorted from normal shape, which method comprises'expanding the. fabric widthwise to an extent to distort the stitches widthwise, mechanically collapsingthe stitches from their distorted condition to an extent to condense the fabric both lengthwise and Widthwise and cause substantial overlapping and close intermingling of the stitches, thus reducing the fabric to smallerthan-normal size, and calendering the fabric to 8 finish thesameand to expand thefabric toits normal size.

3. A method of treating wet or moist longitudinally-stretched knitted fabric whereof the stitches are elongated longitudinally and distorted from normal shape, which method comprises expanding the fabric widthwise to an extent to distort-the stitches-widthwise, mechanically collapsing the stitches from their distorted condition to an extent to condense the fabric both lengthwise and widthwise andcause-substantial overlapping and close intermingling of the stitches, thus reducing the 'fabric to-smallerthan-normal size, drying the fabric concomitantly with the stitch collapsing action, and calendering the fabric tofinish the same and to-expand the fabric to its normal size.

4. A method of treating wetor moist stretched knitted; fabric whereof the stitches are distorted from normalzshape, which method comprises sub! jecting the fabricto agitation effective to collapse the stitches fromtheir distorted condition, continuing such agitation until the fabric iscondensed both lengthwise and-widthwise and the stitches are caused to beoverlapped and closely intermingled, thus reducing the fabric tosmaller-than-normal size, drying the fabric concomitantly with the stitch .collapsingeaction, and calendering the fabric to. finish the same and to expand the fabric to itsnormal size.

5. A method of treating wet or moist longitudinally-stretched knitted .fabric whereof the stitches are elongated :longitudinally and distorted from normal shape, which method comprises expanding the fabric widthwise to an extent to distort the stitcheswidthwise, subjecting the fabric to agitation'efiective to collapse=the stitches from their distortedrcondition, continuing such agitation until the fabric is condensed both lengthwise and widthwiseandthe stitches are caused to'beoverlapped and closely intermingled, thus reducing the fabric to smallerthan-normal size, drying the fabric concomitant- 1y with the stitch collapsing action, and calender: ing the fabric to finish thesame and to expand the fabric to its normal size.

' JOHN. HAMILTON.

ARTHUR A. MEDER, JR.

ReferencesCited in the filed this patent UNITED STATES PATENTS 

